Sympathetic innervation to Moller's smooth muscle in the superior eyelid of the rat normally is derived entirely from the ipsilateral sympathetic chain. Removal of the ipsilateral superior cervical ganglion (SCG) in juvenile and adult rats results in sustained SNS denervation and impairment of Moller's muscle adrenoceptor-mediated contractile response. In contrast, ganglionectomy in neonatal rats results in functional SNS reinnervation from the contralateral SCG. Contralateral reinnervation is beneficial, since contractile responses show less deficit and ptosis is markedly attenuated relative to older preparations in which reinnervation does not occur. The objectives of the present study are to characterize anatomical and physiological aspects of the contralateral projection, determine the cellular mechanisms responsible for enhanced neuroplasticity in neonatal rats and determine if contralkateral reinnervation occurs in other end organs. The specific aims of the project are to; 1) define the optimal age and time course for smooth muscle reinnervation, 2) determine the structural and functional correlates of contralateral reinnervation (LM histofluorescence and EM cytochemistry to assess density of innervation and neuro-muscular relationships; HRP transport to analyze numbers, size and distribution of ganglion cells; functional analysis of reflex contractile responses to selected stimuli), 3) determine effects on smooth muscle maturation using physiolgical/pharmacological methods to assess function and quantitative LM to analyze muscle volume and cell numbers, 4) determine effects of perturbations which may modify neonatal neuroplasticity, and 5) examine other end organs to determine if contralateral innervation following neonatal denervation is more widespread than realized. This study will attempt to ascertain the mechanism of enhanced neuroplasticity in the neonatal SNS which has not previously been studied. Furthermore, it will provide information of clinical relevance regarding possible amelioration or treatment of cervical SNS lesions (Horner's syndrome) for which adequate therapy does not exist.